Wheel steering mechanism



y 1949- s. KRILANOVICH 2,470,496

WHEEL STEERING MECHANI SM 3 Sheets-Sheet 1 Filed Sept. 22, 1947 16 w 3nventor 5TEPHEA/ KQ/LANO V/CH (Ittotneg May 17, 1949. 5. KRlLANOVlCH 2,470,496

WHEEL STEERING MECHANISM Filed Sept. 22, 1947 3 Sheets-Sheet 2 3 m g g STEPHEN KE/LANO V/CH 4 C(ttorneg y 1949- s. KRILANOVICHV 2,470,496

WHEEL STEERING MECHANI SM Filed Sept. 22, 1947 5 Sheets-Sheet 5 nventor 57EPHEN KR/LA/va V/CH (Ittorneg camera for movement relative, 1 scene "being photographech The: flexibility of movement of the camera,- .-great =variety ofxsuch effects, but such movement 'must be accomplished without jar or abrupt changes of direction.

Patented May 17, 1949 2,470,496 WHEEIJ s'i EfJRING' MECHAnIsM StebheriKrilifii'dirih;Northfibllywoodtflalif. Apiilimtionseiimiiber 22, 1947, serieiNo-ifiimn '1 Clainis. (015280- 91) T1 This inventionrelates to means for steering the wheels of a daily or truck and deals more particularly with such means incorporated'in a dolly on which is. mounted a motion picture-camera.

In shooting motion pictures, many desired :technical 'effectsare obtained by mounting the to thesubject or of course,- allows; for V a An object of thex=present invention, therefore,

is to:provide:a;- dolly, for. the'morez-particularipur- I pose' of mountinga,:motiompictureqcamermwhich is i supported on wheelsw'a'ncl embodying means whereby said wheels may;.1se1ectively. be' steered'ato provide universal and smooth movement of the 16011 and the camera; thereon.

' Another "rob'ject of the -invention- :is stoi'provide can be directed-"for movement ofthe dolly finrany --dire'ctionin a straight line forwardg-backward, transverse-'or--'oblique.

"Another object"offlthe 'invehtionfis -to provide "a *delly'inwhieh thewheelsthereofean besteefed for movement of the irony in an *ercuat'e "path arounda**point outside of the wheels.

fA further objectof theinvention"isitohifovifie eJ-dolly in whichthe wheels thereof can'besteered for circular movement of theddlly about'anoiht central of the "wheels.

sun furtherfiobject of thefihvention is topm- Videthe wheels" of ariolly with noveYtransmi'ssion means whereby said "wheels may, 's'el ectivelyibe steered to like angular positions; to tangentialjhm "sit'ions with respect to arcs generated about f a point outside mewheen, and to"ositions'itahgent to' a circle generated. about a some central ofthe wheels whereby univ'er'selmovementof thed'olly is obtained.

whereby thd'o lly' is adapted. to track on its wheelssmoothly and. without jar.

My invention also hasfor its objects to provide 'such'rn eans that are-.bositive in opme'ongdonvenient-in use, easily installed alworl'cing page tion andeasily disconnected therefrom, economieral-ly, a: platform spective front and rear :ofoneside: of safdoplat- =zontallypivotal -braicket and connected: toe-the platform, I a 1 transmission ytivelyconnecting-said transmission unit and the brackets 1 6.

; rangementsof parts,.whic h will.

t e P s t: nven iwi. wh

cording to t prs e ti e i n.

-2-- 2 of Fig l 'with the "abouts-"point withingthe wheels.

to t a k. lon a. dimension oi-the dolly. n

the iIrlensm ss onn n partsg in. the position they cal of f=manuiactureflelativelysimblej' ahd xof'genra l su r riiwsd.se iriesabi i r,.

h nv fiqn -e so construction ang hovel, co 'bifnations an A .93- i leir ar n r epiathei j ing'q t i i im-p e r; h e is sme t s qwg f e is c t e amerely; e i be -Q s .1

is Tgivenby nwa'y' of e tes illustration or example only. In e d in s: i ir e neei hem Fig. 1 is; a s deelevational view of a) dolly ec- Fig. 2' isaflplan sectionalview therejr a dolly; wheels, in full in outsidethe-wheels and, innot-dash lines to track Fig. .3 is w er l wiwit l th f i ywi t it line oblique to the long-ituilinal Fig. t is anenlarged-plansectional 1 471 9? Ei tl t fi said transmission ini-the .-pwitiops itsiparts as- .sume with the wheels aligned asnn- Big. 1. a

F is -s mila Vi w ho -tbei e im si assumewith the-wheels as m the full'line-positmnof Fig.2.

Fig; 6 is a'schematicview showingithe iiifierent :angular relative: movementsof-wpart resulting in -the iull'lineposition of the wheels-inFigI .2.

Fig. 7 is'a further enlarged cross-sectional view as taken on line ofv Fig.4.

'Eig. '8 "is a cros's sectionalwiewas'ltaken on line "8--8 of Fig 7.

'The "dolly which is illustrated. comprisesi g'hfliiy-wheels l l andEIZFat thefreformywheels ;l 3 and I 41 at therespective front and ,rear ofthe othensiderof theplatform fiamaxle' ji 5 for each of said wheels, a vertically disposed horil 6 mounting each axle unit 1 1 ,and chain-and sprocket; means? I 8 Tenem- In th e present instanceqeach -wheel Hip |'3 and -l 4- is"shown-sas;a double -wheel mountedflbn "the respective axles l 5.- and it 'will be.:=unglerstood that these may be single wheelsiif desired i-A'lso, the wheels are shown as free-running- -and the 5 hr 9 e.= mo e b P sh -t e. em ie it is evicient that one;oy-nnore of said wheels (may 'be driven by suitable "motive power.

. ter is formed as a spool for engagement shafts 34, 35, 3 6 and moved to engage teeth 56 a the mentioned. shafts, at

' tate in the movement of bars The transmission I7 is enclosed in a casing l9 and the latter is secured to platform It as by studs and preferably at the front end of said platform.

The transmission, centrally thereof, is provided with a control shaft 2| that extends upwardly and, at its upper end is provided with a steering wheel 2'2 whereby said shaft is rotatable in either direction. Within the casing l9, shaft 2| is fitted with a loose sleeve 23 which carries a four-lobed cam 24 adjacent the top wall of the casing, a sprocket wheel 25 beneath said cam, and a singlelobed cam 26 beneath the sprocket wheel. The sleeve 23 is formed with down-reaching clutch teeth 21 for engagement with a clutch sleeve 28 that is slideable on shaft 2| and keyed thereto. On the opposite side of the clutch sleeve 28, a loose sprocket wheel 29 is provided On said shaft 2| adjacent the bottom wall of casing l9 and the latter is formed with upstanding clutch teeth for engagement with the clutch sleeve. The latby a fork 3|, pivoted on a shaft 32, and having an operating handle 33 extending upwardly from the transmission casing toward the steering wheel 22. It will be evident that by suitable manipulation of handle 33, the clutch sleeve '28 can be coupled to the sleeve 23 and the sprocket wheel 29, selectively, whereby one or the other is rotatable with shaft 2|.

Across the transmission casing and extending from the bottom wall thereof through the top wall shafts 34, 35, 35 and 31 are provided. These shafts are, respectively, provided with sprocket wheels 38, 39, 40 and 4| on the portions thereof above the casing. Gears 42 and 43 connect shafts 34 and 35 for simultaneous but opposite rotation, and similar gears 44 and 45 connect shafts 36 and 3'! for similar rotation. However, said four gears are loose on their respective shafts and each, like the sleeve 23, is provided with down-reaching clutch teeth 46 for engagement with clutch sleeve 41 slideably keyed on each of 3?. Thus, the mentioned simultaneous opposite rotation of the shafts is effected only when the clutch sleeves 4'! are of the gears. Each of its lower end is provided with a loose sprocket gear 48 having upstanding clutch teeth 49. Said wheels 48 and teeth 49 being similar to the sprocket wheel 29 and clutch teeth 30. A chain 59 is trained around the sprocket wheels 25 and 48, as best seen in Figs. 4, 5, 7 and 8, whereby all of said wheels ro-. same direction and to the same degree.

The gear 43, in alignment with sprocket wheel 25, is provided with a similar wheel 5| fixed therewith. Similarly, the gear 44 is provided with a sprocket wheel 52. Idler sprocket wheels 53 and 54, One on each side of shaft 2|, are provided in saganar alignment with sprocket wheels 25, 5| and In planar alignment with cam 24, roller discs 55 and 56, one on each side of said cam, are provided. Each disc is freely mounted on a shaft 51 carried by a bar 55 mounted to slide laterally on fixed studs 59 carried by the casing 9. In

' the plane of sprocket wheels 25, 5|, 52, 53 and '54 and freely rotatable on shafts 51 there are provided sprocket wheels "60 and 5|, one on each of said shafts 51.

A bar 62 is arranged to engage cam 26 and to be moved thereby in a direction normal to the 58 and on guide studs 63. Said bar "62 carries a freely rotatable sprocket wheel 64 on a shaft 55 coplanar with sprocket wheels til and 5 A chain 66 is trained around sprocket wheel 25 and around and in driving engagement with sprocket wheels 53, 65, 5|, 64, 52, GI and 54 in such a manner that, upon clockwise rotation of sprocket wheel 25, the other wheels will be r0- tated counterclockwise and that upon counterclockwise rotation of sprocket wheel 25, the other wheels will be rotated clockwise.

A clutch-operating fork 61, engaged with the clutch sleeves t? of shafts 34 and 35, is mounted to rock on shaft 32 through manipulation of a. handle 58 for selective engagement of said clutch sleeves with clutch teeth 46 and 49. Similarly, a clutch-operating fork 69 having a handle 19 is engaged with clutch sleeves 41 of shafts 36 and 31.

The lobes of cam 24 have been designated 12, i3 and 74 and in the normal position of Fig. 4, the roller disc 55 engages said cam between lobes 1| and 12, and roller disc 56, between lobes l3 and 14.

The means l8 comprises a chain 15, is trained over sprocket wheel 38 and over a similar wheel it fixed to the pivoted bracket N5 of wheel I3; a chain 11 is trained over sprocket wheel 39 and over a sprocket wheel 18 fixed on the bracket of wheel l4; a chain 79 is trained over sprocket wheel 45 and over a sprocket wheel 8|] fixed on the bracket of wheel l2; and a chain 8| is trained over sprocket wheel 4| and over a sprocket wheel 82 fixed on the bracket of wheel I I.

Fig. 4 shows the parts of the transmission arranged to have the means It position the wheels of the dolly as in Fig. 1, whereby said dolly is movable to and fro along its longitudinal dimension.

When it is desired to steer the wheels to any oblique position as in Fig. 3, whereby the dolly is movable along an oblique line 83; or to arrange the wheels so they stand at right angles to their initial position, whereby the dolly is movable in a path transverse to the longitudinal dimension of the platform, the clutch handle 33 is moved to shift clutch sleeve 28 into engagement with clutch teeth 35 of sprocket wheel 29. Similarly, both clutch handles 63 and 10 are manipulated to effect coupling of each sprocket wheel 48 with its respective shaft 34, 35, 36 and 31. Now, upon turning the steering wheel 22, in either direction, shaft 2| will turn sprocket 29 and, through chain 55, sprockets 48, in the same direction. These latter sprockets being coupled to their respective shafts 34, 35, 35 and 37, said shafts will turn to turn the respective sprockets 39, 39, 40 and 4|, the respective chains 15, 11, 19 and 8| and, through sprockets l6, I3, 85 and 82, the respective wheels l3, I4, I 2 and H in the same direction. Each wheel will turn a similar amount and the degree of turn is controlled by the amount of the turn imparted to the steering wheel. During this steering movement, cams 24 and 26, and sprocket 25 and those connected to it by chain 56, are uncoupled from their respective shafts and, therefore, stationary.

When it is desired to steer the wheels of the dolly so that the same is movable in an are about a center outside of the wheels, such as the center 34, the three clutch handles 33, B8 and 79 are manipulated to eifect coupling of clutch sleeve 28 with sleeve 23 and of the clutch sleeves 47 with the respective gears 42, 43, 44 and 45, whereby the latter and sprockets 5| and 52 are connected to drive the shafts 34, 35, 36 and 31, respectively.

a l-mace .Wafdly and, "consequentlm sprockets 60 and B I move oii'twaidly(to bu1gechain*86 asishown in 5. *Thusja-sthei'chain"is'inrdved'hy sprocket '25, .that portion thereof trained between sprockets 6G and "5| moves "faster to' impart a "greater angular"rotationalmovement to sprocket 5|? than was "impartedtosprocket 25w thesteer- "As"the above chaimmovementfoccurs; the bight ,fif the chain that is itflifidovel sprqbketwk is reduced in "length' between sprocketsfi I and 52 imi'dercontrol 'ofcam' i lfr-vvhich moves bodily with eam 'za. "This" shortehingbf the' c'hain bight re- "?siilts'in' a; lesser ang'hiarTotationaPmovement oi sprocket 52 the sprocket '6 l merelymaintaining the chain taut. It will be evident that the-chain hight betweemsprockets 53* and" 5 l-"is 'lengthene to cause *i'ncreased rotational "'movement or sproc'ket t'i I and that the-chain night between sprockets--51 aud t? is" shortened to cause arelativelylesserrotational movement-or sprocket52.

Both sprockets 5 l and 52 rotate in the-same Fd'lrecti'on and; because-oi th'eirconnection-to the respective shafts 35"arld" 3 6 "andthe"'respective Wham-connections "11"aiid 19 to wheels "M and "12, #said whe'els are 'respectivelyrotated "on 'brackets tii -an"arigu;lar amount comparable-to that of the respective" sprockets. The pairs of wears- 42mm 43, and M and QE cau'sesimiIar bue'oppos-ite rotationofshafts* 34and3T"andof wheels ltand H res'pe'ctively.

*Fig. 2 shows the fu'l1' line'p0siti'on"of thewheels as they are =steered""by a clockwise rotation of *the*steering"whee1and of cam '24, inwhich case, the chain bight between sprockets 54 enwiz *inoves the latter sprocket through "a' greater angular movementwith 'ar'resultant lesser angular theyerrient of sprocket?!I.

-It* virill 'be evident that the lobes l I ;"|2,' T3'1'and "-14 mi cam 24 are "designed tot merely""pres's -=sprockets'- 6t and" 6 l"oiltvvai"dly' a'nd that theratio of the angular movementofsprockets 5 |arfd"52 'is a f-uncti-on' or the degree vvith'v'vhichf the chain higl-it ti'ained oversprocket i liesseris. Thisratio cant-then be resolverfawanihverse ratio of angle moi Fig: eanemQearorr-i ra By =cor'1su1tihgFig. 6,'it""will beiseen that for eacrr uniform incrementoranginar movement of one sprocket the other hagnot" only a "lesser "increment of angular'niovment'but said latter increments are first "greater; then "decreasingly smallenarrd then increasingiyrlarger.

of the dolly are desired to be'sudh'that theywiH "smoothly" track about a incint" 84, said angular positions "are "directly "'reIatedftO '2 the transverse *spac'ingof the front and rear wheels. Closer "spacing or said'wheels" entails a lesser difference in -the angular iri-crerrients "of :movement of the wheels and, 1 conversely, a "greater spacing, a greater difference insaid angular increments.

assumin the wheel-spacing dimension "'88 to oe 28 /2 inche the' fbl'lfiwiflg' table, based on Fig. '6,'-s'-hows in thefir'st columnytheuniform inerement of ang ular movement ofsproketS l ,in the second colmirnn, the vaiia 1e increment "of angman movement 1 or sprockt' fi, and in the third wolumn, the "corresponding -'-"suecessive differences in movement ofthe' latter'sproekt.

5 Sprocket 51 *SprocketSZ Difierence Degrees Dcgrees -Degrees 1 i0 SiO 8.0 "20 13.5 5.5 30 1 17.7 4.2 -10 40 "21.0 3.3 '24 0 -3.-0 $6.8 2.8 --29.5 2.7 ,-a2.2 2.7 35.4 3.2 39'. 5 4'. l 43.7 4.2 15 50.3 6.6

The figures of thelast two columns are, necessarilysomewhat approximate and I are primarily "intended to show-the variability of the move- .ment of one sprocket during. the uniform move- -ment" of the other. The; point can reside anywhere along line'89 and may approach the center 90 of the dollyand'yetthe'wheels can be positioned-so that said dolly: arcuately tracks about said point.

-It'wi11 be noted that thelast figure for sprocket 5| is 125.2 and for sprocket 52, 54.8. -By tuming the steering wheel: 22. in either direction, assuming a counter-clockwiserotation of said steering wheel and continuing the rotation until sprocket 52 has rotated-50;2,=the-whee1s Hand l2,=as: shown by the dot-dash lines; will be rotated to angular positions of-likeidegree, but each'in the opposite direction. For ther-spacing ofathe Wheel centers indicated these wheels will-now be tangent to a circle generated about-the center Elli of the-dolly. During'this angular movement ofzsp'rocketEZ, sprocket 5| will-rotate'through annarc of 125.2 to'bring' wheels 13 and-l4 also tangent'to said circle. The dolly can then-be readily rotated aboutthe centerpoint 90.

By'suitably mounting a camera at the centerv 90, it will be seen that said camera can be'moved sin any straightline :toward, away fr0m,-transversely and obliquely'withrespect to 'a subject being shot; that-said camerazcan be moved to circle a subject; and th'ahsaid camera canibe moved'to snap ascene'or other panoramic area.

lt'vvill be further seenxthat the: mentioned unirvers'alsmovement of 5the= camera and of the dolly is effected smoothly and with a jar.

While I have illustrated and described what-I nowregardas the preferred embodiment'oi my invention, the construction is, of course, subject to modificationswithout departing from the-spirit -andscope-of my invention. 'L -therefore-do not --wish .to' restrict myself to the particular form 'of construction illustrated and described, but desire '-toavail -myself hi all modifications that may fall within the scope 0f the appended'--claims.

Having thus described"myinvention, what I claim and desire to-secureby Letters Patent "is:

1. In combination, a platformyfourhorizontally pivotab Wheels=si1pp0rting sa-i'd" pIatiOrrn'and arranged in =-pairs-along each side of said platferm, a transmissionf Steeririg=ineans for manuan controlling-said transmission, means con- 70 meetingsaid-Stering rriiaans With' said wheels'for "steering one pair thereof to a position tangent to an are generated about a point located "along a line midway between "said"'1atte'r pair; cr; .wnee'1s ean d for simnltaneously steering the otherf'pairiof 75 "Whls toa positron-tangenttoan arc generated about said point and passing through the pivots of the latter pair of wheels, clutch-controlled means for selectively connecting the steering means and the means connecting the same to the wheels to steer all of said wheels simultaneously in the same direction, and additional clutch means for selectively connecting the steering means and the means connecting the same to one pair of wheels to steer the latter to a position tangent to a circle generated about a point central of all the Wheels and for subsequently connecting the steering means and the means connecting the same to the other pair of wheels to steer the latter to a position also tangent to said circle.

2. A transmission comprising at least two shafts; a sprocket wheel on each shaft, a steering post; a sprocket wheel thereon, a cam on the steering post; a pair of sprocket wheels mounted for opposed movement undercontrol of said cam; a second cam on said steering post, and a sprocket wheel mounted for movement transverse to the movement of the sprocket wheels controlled by the first cam; said sprocket wheels all being coplanar; and a wheels whereby they all rotate in unison upon manual rotation of the steering post; and whereby the mentioned opposed movement of said pair of sprocket wheels effects a greater distance of travel of that portion of the chain engaged with the sprocket wheel of one of said shafts, with a corresponding greater angular travel of the latter sprocket wheel and its shaft, than is imparted to the chain by the mentioned manual rotation of the steering post and its sprocket wheel.

3. A transmission comprising at least two shafts; a sprocket wheel on each shaft; a steering post; a sprocket wheel thereon; a cam on the steering post; a pair of sprocket wheel mounted for opposed movement under control of said cam; a second cam on said steering post; and a sprocket Wheel mounted for movement transverse to the movement of the sprocket wheels controlled by the first cam; said sprocket Wheels all being coplanar; and a chain trained about the sprocket wheels whereby they all rotate in unison upon manual rotation of the steering post; and. whereby the mentioned opposed movement of said pair of sprocket wheels effects a greater distance of travel of that portion of the chain engaged with the sprocket wheel of one of said shafts, with a corresponding greater angular travel of the latter sprocket wheel and its shaft, than is imparted to the chain by the mentioned manual rotation of the steering post and its sprocket wheel; and whereby the transversely movable sprocket wheel, under control of the second cam, moves to effect a shortening of that portion of the chain extending between the sprocket wheel having the greater angular travel and the sprocket wheel on the other shaft to reduce the travel of that portion of the chain engaged with the latter sprocket wheel, with a corresponding lesser angular travel in the same direction of said latter sprocket wheel and its shaft.

4. A transmission comprising at least two shafts; a sprocket wheel on each shaft; a steering post; a sprocket wheel thereon; a cam on the steering post; a pair of sprocket wheels mounted for opposed movement under control of said cam;

movement of the sprocket wheels controlled by the first cam; said sprocket wheels all being coplanar; a chain trained about the sprocket chain trained about the sprocket wheels whereby they all rotate in unison upon manual rotation of the steering post; and Whereby the mentioned opposed movement of said pair of sprocket wheels effects a greater distance of travel of that portion of the chain engaged with the sprocket wheel of one of said shafts, with a corresponding greater angular travel of the latter sprocket wheel and its shaft, than is imparted to the chain by the mentioned manual rotation of the steering post and its sprocket wheel; and whereby the transversely movable sprocket wheel, under control of the second cam, moves to effect a shortening of that portion of the chain extending between the sprocket wheel having the greater angular travel and the sprocket wheel on the other shaft to reduce the travel of that portion of the chain engaged with the latter sprocket wheel, with a corresponding lesser angular travel in the same direction of said latter sprocket wheel and its shaft; a second pair of shafts; and gearing connecting the latter and the first-mentioned shafts for rotating the second pair of shafts in a direction opposite to that of the first-mentioned shafts.

5. A transmission for steering the four wheels of a vehicle comprising at least two shafts; a sprocket wheel on each shaft; a steering post, a sprocket wheel thereon; a cam on the steering post; a pair of sprocket wheels mounted for opposed movement under control of said cam; a second cam on said steering post; and a sprocket wheel mounted for movement transverse to the movement of the sprocket wheels controlled by the first cam; said sprocket wheels all being coplanar; a chain trained about the sprocket wheels whereby they all rotate in unison upon manual rotation of the steering post; and whereby the mentioned opposed movement of said pair of sprocket wheels effects a greater distance of travel of that portion of the chain engaged with the sprocket wheel whereby the transversely movable sprocket wheel, under control of the second cam, moves to efiect a shortening of that portion of the chain extending between the sprocket wheel having the greater angular travel and the sprocket wheel on the other shaft to reduce the travel of that portion of the chain engaged with the latter sprocket wheel, with a corresponding lesser angular travel in the same direction of said latter sprocket wheel and its shaft; a second pair of shafts; gearing connecting the latter and the first-mentioned shafts for rotating the second pair of shafts in a direction opposite to of the first-mentioned shafts; a vertically disposed horizontal pivot for each wheel; and chain and sprocket means operatively connecting the four mentioned shafts and each respective wheel pivot.

6. In a wheel steering device, a pair of sprocket wheels; a steering post; a sprocket wheel on said post; a chain trained about said sprocket wheels; and means effective, upon manual rotation of the steering post, for lengthening those portions of the chain extending between the sprocket wheel on the steering post and each of the other sprocket wheels, and, correspondingly, shortening that portion of the chain extending between the pair of sprockets, whereby one of the latter sprockets has a greater and the other has a lesser angular movement than is manually imparted to the sprocket 0n the steering post; the latter means comprising a cam on the steering post; a sprocket wheel, one on each side of the cam and each engaged with the first-mentioned portions of the chain; means engaged with the cam for moving the latter sprocket wheels in a direction to effect lengthening the mentioned chain portions; and means responsive to the pull thus exerted on the chain to elfect foreshortening of that portion thereof between the pair of sprockets.

7. In a wheel steering device, a pair of sprocket wheels; a steering post; a sprocket wheel on said post; a chain trained about said sprocket wheels; and means effective, upon manual rotation of the steering post, for lengthening those portions of the chain extending between the sprocket wheel on the steering post and each of the other sprocket wheels, and, correspondingly, shortening that portion of the chain extending between the pair of sprockets, whereby one of the latter sprockets has a greater and the other has a lesser angular movement than is manually imparted to the sprocket on the steerin post; said latter means comprising a cam on the steering post; a sprocket wheel, one on each side of the cam and each engaged with the first-mentioned por- 25 tions of the chain; means engaged with the cam for moving the latter sprocket wheels in a direction to effect lengthening the mentioned chain portions; and means responsive to the pull thus exerted on the chain to efiect foreshortening of that portion thereof between the pair of sprockets; said latter means comprising a second cam on the steering post, a sprocket wheel movable thereby and engaged with the latter portion of the chain.

STEPHEN KRILANOVICHZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,255,775 Mueller Feb. 5, 1918 1,866,393 Brooks July 5, 1932 2,001,647 Alt May 14, 1935 2,232,015 Skok Feb. 18, 1941 2,423,266 Stokes July 1, 1947 FOREIGN PATENTS Number Country Date 451,813 Great Britain Aug. 12, 1936 

